The present invention relates, in general, to switch devices and more particularly relates to switch devices useful in hostile environments.
Devices within the scope of the present invention belong, in general, to a broad classification of spring return indicator type switch devices which are moved from a first position to a second position by an occurrence such as the presence of a moving object. Devices within the general scope of the present invention, that is bias or switch devices are useful in numerous of applications from a simple spring loaded cam operated switch to complicated switches which are useful in certain hostile environments.
Devices of the type contemplated by the present invention are useful in extremely hostile environments such as to detect the movement of a roller conveyor belt to shut down a conveyor line to prevent escape of the belt from the retaining rollers for example in mining, mineral processing, or transporting coal.
In such applications it is particularly important that the switch device be of rugged construction and capable of induring the most agueous service. Additionally, the switch devices in such applications encounter hostile environments such a sulfur compound which easily penetrate many mechanical devices. Accordingly, it is important that devices for such service be completely sealed from the atmosphere and have a minimum of number of moving parts located outside of any enclosure in which the operating parts are housed to minimize the likelihood of the effects of the corrosive atmosphere.
Examples of devices provided by the prior art for such application include Ramsey Pro-Line.TM.safety cable pull switches, as well as other similar devices which operate a switch means. In general such devices do not provide means for protection of the switch device from over travel or rapid movement of the actuating lever which is usually associated with such devices. Similar, devices are also manufactured by "Square D" and others.
No prior art arrangement is known which provides the multiple advantages of switch means within the scope of the present invention.